This invention relates to anomaly diagnosis of the equipment, and more particularly to improvement of reliability of diagnosis of a plant having a circulating system in which a fluid circulates.
Heretofore, technologies for anomaly diagnosis of equipment including a circulating system have been revealed in JP-A-64-46694, JP-A-62-223905, and JP-A-59-60293. JP-A-64-46694 concerns a method in which a quantity under observation is measured, and from its output level, anomaly is diagnosed. In a region where a radioactive level is high such as a nuclear reactor primary system, this method depends very much on the soundness of the measuring instrument.
JP-A-62-223905 discloses a method in which large threshold values are set for output of process quantities in steady state, and when a process quantity exceeds its large threshold value, threshold values of other process quantities are lowered, and diagnosis is conducted.
JP-A-59-60293 relates to a circulating system and describes a method for diagnosing anomaly from correlation between two quantities under observation (conductivity and pH) concerned with water quality.
In the above-mentioned prior art, when anomaly occurs, decision cannot be made whether the anomaly is a true anomaly or an anomaly originating in the detector caused by noise or the like. Especially when the detector can detect anomaly only by a transient signal, it is impossible to confirm whether the anomaly is a true anomaly. Therefore, the problem with the prior art is that anomaly cannot be diagnosed with high reliability.
The method in JP-A-59-60293 can detect ions when they are produced by anomaly of the equipment, but cannot detect particulate substances such as cladding.